1. Field of the Invention
This invention relates to improvements in disc pulverizers and particularly to heads useful on disc pulverization machines.
2. Prior Art
Pulverizer heads are generally of a type having a bowl with an annular ring within the bowl and a solid cylinder within the annular ring, both of which are moveable within the bowl and are used by placing a sample or charge of mineral or rock to be ground or pulverized within the bowl, placing a lid on the bowl and then the bowl on a shaker and oscillating it, such that the sample is crushed between the ring cylinder and bowl and ground finely.
The problem with such ring and cylinder pulverizer heads is, however, that the sample size, which can be prepared by such a device, is very small and if too much sample is put into the pulverizer head the ring and cylinder become clogged up and do not move in relation to the bowl and hence do not grind up the sample. Also such ring and cylinder grinder do not efficiently grind up larger pieces of sample and it is often necessary to place sample through a laboratory jaw crusher first to get it into a suitable size for pulverizing. SUMMARY OF THE INVENTION
It is the aim of the present invention to provide a pulverizer or grinder head which will overcome at least some of the above problems by being able to accept a greater size range of material in the charge and larger charges without clogging and jamming.
It is to be understood that pulverizers or grinders of this type comprise a power driven platform adapted to be oscillated and upon which a grinder bowl may be clamped for the oscillatory motion. This specification is directed particularly towards the bowl or head for the grinder and the configuration of the disc within the bowl and hence it is to be understood when the term "head" or "grinder head" is used it refers to a bowl of the type adapted to be clamped to an oscillatory platform. The word "charge" will be used in this specification to designate the sample placed or to be placed within the bowl whether it be rock or mineral or other substance that is desired to be ground to a smaller particle size.
It should be noted, too, that the present invention also relates to a laboratory rock grinder heads of larger sizes such that the head is not easily removable from the oscillatory platform and hence is mounted permanently thereon. In such a case suitable means may be provided to clamp the lid to the bowl.
The invention may therefore be said to reside in a laboratory rock grinder head comprising a lid, a bowl and a grinder disc within the bowl characterized by the bowl having a substantially cylindrical shape and having a shaped surface between its internal side and its internal base and the disc being of a solid cylindrical shape and including a correspondingly shaped rim on its lower edge adapted in use to co-act with the shaped surface of the bowl.
It will be seen that by this invention there is provided a laboratory grinder head in which the disc can not only oscillate and orbit within the bowl to crush a charge but also with the bevelled surface on the disc co-acting with the bevelled surface on the body of the bowl then the disc can ride up over a charge within the bowl and the weight of the disc, in conjunction with its oscillating and orbiting motion, can crush larger pieces and the disc will not become jammed if it comes up to a larger piece because it will ride over the piece and assist in cracking the charge.
In one preferred embodiment the shaped surface comprises a curved surface and the correspondingly shaped rim comprises a curved rim.
In an alternative preferred embodiment the shaped surface comprises a straight angular bevel between the internal side and internal base of the bowl and the corresponding shaped rim on the disc comprises an angular bevel.
In a preferred embodiment of the invention, the disc may further include at least one aperture through the disc in the direction of the cylindrical axis.
Such an aperture or apertures may be circular and may have a diameter of from 15 to 40 percent of the diameter of the disc.
It has been found that the addition of the aperture in the disc assists with the grinding action, as sample which has been ground can move up through the aperture as the disc is orbiting and oscillating such that sample or charge underneath the disc is continually being replaced by a type of "pumping" action caused by the disc orbiting.
In a preferred form the aperture may be circular and may taper from the top surface to the bottom surface of the disc.
Such an aperture may be offset from the centre of the disc.
The bottom surface of the disc may also have a very slight conical shaping.
By this conical shaping when the rim of the disc rides up onto the angled surface on one side of the bowl then one portion of the disc base will be almost parallel to the base of the bowl to provide a fine grinding surface.
In a further preferred embodiment the angled surface in the bowl may make an angle of between 20 degrees to 35 degrees to the planar base of the bowl.
Similarly, the bevelled rim of the disc may make an angle of from 20 degrees to 35 degrees to the base of the disc.
In a preferred embodiment of the invention the angled surface within the bowl may be comprised of two angular portions, an inner portion and an outer portion, with the inner portion being of a smaller angle to the planar base than the outer portion.
The bowl may include an outer shell and an inner liner with the inner liner being made of a harder wearing material than the shell.
By this means a relatively economic main bowl may be made with replaceable liners to be replaced as wear in the bowl occurs.
The disc may further include a stepped shoulder on the upper rim. This stepped shoulder may assist with crushing of larger rock samples as it catches larger pieces between the edge of the rim and the side of the bowl as the disc oscillates and orbits about in the bowl.
The diameter of the disc may be from 70 to 90 percent of the inner diameter of the bowl.
It will be seen that by this invention there is provided a rock grinder head which is of relatively simple construction but which can efficiently grind rock samples.